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Coasting with throttle closed ... how big a deal?
Posted: 05:49 pm Aug 10 2011
by turtle
Hi all ... I am still new to off road riding but I am finally getting to ride my KDX a bit. I mostly ride in an area with tight woods trails that is somewhat hilly. I read on here that coasting down hills for engine braking or slowing after a high speed run with the throttle closed is a bad idea. This made some sense to me because no throttle = fuel and no fuel = no lube. How big a deal is this and what technique do you use to work around it if necessary - clutch in? Throttle blips to feed some fuel/lube? Or do you just ride it normal and not worry about it? TIA.
Posted: 05:59 pm Aug 10 2011
by scheckaet
there was a tread not long ago about this. Look it up.
I think the consensus was to be safe: long downhill, blip and / or clutch in with blips.
Posted: 07:01 pm Aug 10 2011
by turtle
I read the thread a while back. Consensus seemed to be lacking which is why I was asking again. I will reread it tho.
Posted: 07:17 pm Aug 10 2011
by Julien D
yeah. when a subject like that gets no consensus the first time around, most likely neither will it the second time around. There's a lot of factors involved, and it may very well be safe if your bike runs in such a way as to have plenty of residual oil in the crankcase. However, to be safe, just don't do it for prolonged periods. Why on earth would you need to? A little here and there is normally going to be fine.
Posted: 08:32 pm Aug 10 2011
by rbates9
Moderation I think is key. A very long hill you might want to clutch and rev a little. Shorter hills just go with it.
In the last thread on this it was split down the middle, but it is your bike that you pay to fix.
Posted: 09:29 pm Aug 10 2011
by turtle


juliend wrote:yeah. when a subject like that gets no consensus the first time around, most likely neither will it the second time around. There's a lot of factors involved, and it may very well be safe if your bike runs in such a way as to have plenty of residual oil in the crankcase. However, to be safe, just don't do it for prolonged periods. Why on earth would you need to? A little here and there is normally going to be fine.
OK guys. Points taken. Thanks.
Posted: 09:38 pm Aug 10 2011
by scheckaet
question: how many of you know or have heard of a lean seizure in such situation?
just wondering.
If I had lots of down hill or needed to coast a lot, I'd blip the throttle every once in awhile.
I already do that anyway to keep the rev up since I tend to run on the pipe a lot and I also got used to it on my (4 strokes) street drz to reduces the engine braking.
Posted: 09:45 pm Aug 10 2011
by rbates9
I have never heard of it but, the logic of closed throttle and higher revs keep's me in the practice of blipping the throttle. Personal preference, better safe then sorry.
No, never heard of a problem. Yes, going to stay on the safe side.
I don't think there is any way to test the effects any more than what oil or ratio to run.
Posted: 02:15 am Aug 11 2011
by Mr. Wibbens
IMHO, If the motor is revving it is obviously pulling in more fuel
Posted: 03:54 am Aug 11 2011
by paulkdx220
i've heard that piston ring float/flutter is a result of higher revs with a closed throttle which wears the rings and the piston ring lands.
Posted: 06:42 am Aug 11 2011
by Julien D
Seen it twice.
Well, one seizure (my bike) and one kersploded main bearing (buddies bike). However, there may have been something else going on in mine. No other explanation for his.
Posted: 08:04 pm Aug 11 2011
by David_L6
Coasting down a short hill isn't going to hurt anything. A really long hill, I'd pull the clutch and blip the throttle.
Where you may have something to worry about is getting out of the throttle suddenly and completely after a long wide open run.
What we do with boat motors is hit the enricher (kind of like an accelerator pump - used as a choke during starting) if the motor has one or slowly back out of the throttle. Don't just chop the throttle or you risk lean seize.
Posted: 08:18 am Aug 12 2011
by fuzzy
^^ Indeed, those siesures are much more common
Posted: 12:49 pm Aug 12 2011
by Mr. Wibbens
If coasting down a long hill will cause a motor to seize, mine should have been seized a long time ago
Posted: 03:16 am Aug 21 2011
by Brian
I think the idea of a 2stroke seizing with the throttle closed came from the old air cooled engines. If they were going wide open like in desert racing and the rider rolled off the throttle the very hot piston was prone to seizing. I think it's largly a non-issue with modern era water cooled engines.
That being said...on long down hills I either put the bike in neutral and coast or put it in a taller gear like 4th, 5th or 6th (depending on speed) if I wan't to keep the engine running for a quick blast of power.
Posted: 08:26 am Aug 21 2011
by Julien D


Mr. Wibbens wrote:If coasting down a long hill will cause a motor to seize, mine should have been seized a long time ago
Pretty sure I seen your not too old crank bearings destroyed in the not so distant past.....
No?
I'm sure it was purely unrelated.